Generate warnings/errors when injected interface contains methods without implementation

[Earthcomputer]

Minecraft Development for IntelliJ plugin version

2024.3-1.8.2-539

Description of the feature request

Interface injection has an issue where if the interface doesn't provide an implementation of the method, then when you try to call that method on a non-abstract class, javac will generate a compile error because it can't find any concrete implementation of the method. However, intellij doesn't detect this compile error.

To mitigate this issue, I think we need:

• An error when a method is called on a concrete (non-abstract) type but there is no concrete implementation of that method found at compile time.
• A warning on any method without an implementation in an interface which is used in interface injection.